1. Technical Field
The invention relates to motor vehicle body assembly and more particularly to a system and method of bus body assembly allowing differentiation in configuration using standard body sections.
2. Description of the Problem
Operators of coaches and busses, particularly school busses, often demand specialized body configurations in terms of the location for exit locations and types, body length, engine location (e.g. front engine, rear engine and conventional) and roof height. The current practice for bus construction provides for assembly of a body frame on top of a chassis and then applying a skin over the body frame. This process requires first building a floor structure as a foundation. Then roof bows, stringers and drip rails are raised on the floor assembly to make the body's skeleton. Next, outer and inner sheet metal panels are applied to the skeleton enclosing the body. Building vehicles in this manner to meet differing customer requirements has demanded custom layout, specification of and cutting body elements to fit the custom requirements. All of this variation minimizes the opportunity for use of repetitive construction techniques and makes automation of assembly difficult.
Automated assembly is made easier by application of a modular manufacturing strategy. Modular manufacturing strategies typically deconstruct a product line (including variations) into discrete sub-assemblies (modules), usually located with some degree of arbitrariness. When the modules are combined in various numbers and arrangements multiple product configurations are possible. This type of sub-assembly typically does not exhibit what is termed “functional cohesion”. An example of a sub-assembly module for a motor vehicle is the vehicle engine. An engine is part of a vehicle drive train and is regarded as a standard module in automotive and truck design. It is not a functionally cohesive module, however, because it cannot perform its intended function without a compatible cooling system, fuel system and transmission. When the engine is changed all of the associated drive train sub-assemblies are subject to change to accommodate the change of engine. A functionally cohesive module tolerates changes in other modules but still performs its function.
Where and how demarcations are made in defining sub-assembly units can control how functionally cohesive a sub-assembly is. A bus body may be divided into various kinds of sub-assemblies and remain “modular”. For example, a possible modular bus body might have floor, front end, side, rear end and roof modules. To accommodate customer requests for busses of different lengths the side, roof and floor modules would have to provided in different lengths. The sub-assemblies would lack cohesion. As a consequence, synchronization would be required in delivery of the parts for assembly, adding complexity to the manufacturing process.